Ingot mold for steel ingots



Jan. 21, 1936. J, E PERRY 1- AL 2,028,243

INGOT HOLD FOR STEEL INGOTS- Filed July 5, 1923 '5 Sheets-Sheet 1 1 FLI? T films INVENTOR .fon Efirry and William! 'lamam' By I liATTORNEYJan. 21, 1936. J. E. PERRY ET AL meow now FOR STEEL INGOTS J. E. PERRYEl AL 2,028,243

INGOT MOLD FOR STEEL INGOTS 2 Filed July 5, 1923 s Sheets-Sheet 5 al' lv a w WW w 5 w a m Q .N. A 1 71/ 1 1 .r 5 1 wi o v 1 4 a 1 all/l! zWnflfififl a w 7 I F w 1 7/ a Q /04 ml z/ r wfi flfifl fa M V/ MV/ V Yll n 6 7 Jan 21, 1936 Patented Jan. 21, 1936 UNITED STATES PATENT OFFICERamage, Girard,

Ohio, assignors to Valley Mould and Iron Corporation, Hubbard, Ohio, acorporation of New York Application July 5, 1928, Serial No. 290,329

11 Claims.

The present invention relates broadly to the metallurgy of steel andmore especially to ingot molds for the production of steel ingotswithout surface defects or undesirable crystallization adjacent thesurface of the ingot.

Molten steel when poured into an iron mold first forms a very thin skinof fine grain crystals and then columnar crystals at substantially rightangles to the mold which grow inward under the influence of the chill ofthe mold, and finally axial crystals extending substantially parallel tothe mold wall complete the freezing of the ingot. Since molten steel hasa greater volume than solidified steel, the frozen skin of the ingotadjacent the mold wall contracts and pulls away slightly from the matrixface of the mold wall. The ferrostatic pressure of molten steel in theingot as well as shrinkage stresses exerts an internal pressure againstthis skin tending to strain and stretch it. In view of the fact a planeflat surface cannot elongate without stretching, the skin of the ingotmay break and form external cracks. Since the bottom of the ingot coolsrapidly some distance upward from the stool, the sides of the ingot in azone above the cool base portion remain relatively hot and the skin onthe ingot in this zone is therefore relatively thin. This is partiallydue to the fact that the ingot in shrinking pulls away from the sidewalls and interrupts the conductivity of heat to the side walls, andpartly due to the bottom being cooled more than the sides because of theadded chilling effect on the bottom due to the stool. As the mass ofmolten metal increases during pouring, the ferrostatic pressure of themolten steel may stretch this thin skin out against the side wall of thematrix and wedge the ingot to the mold or it may even cause a breakthrough the skin in this zone of thin skin above the base of. the ingotand a small leak of molten steel from the interior of the ingot throughsuch breaks will cause a. protuberance or button of steel to formbetween the skin of the ingot and the side wall of the mold. This buttonor protuberance quickly freezes and wedges the ingot tightly against themold at this point. In eithercase, the vertical shrinkage of the ingottends to lift the base of the ingot from the stool and cause the bottomportion of the ingot to hang suspended from the wedged portion. Thiscauses horizontal cracks in the weak skin adjacent or beneath thebuttons or projections-referred to. These various surface cracks in thesteel-ingot are very undesirable in that oxidation occurs for the depthof the cracks and defects are thereby formed in the finished finalproduct.

The present invention overcomes the difllculties of the prior art byproviding longitudinally extending recesses in the side walls of themold which form salients on the ingot that are joined by non-salientportions. These salients on the ingot preferably are in the form of lowheight waves or corrugations with the salient portions having largerradii than the non-salient portions that are between the salientportions. With salients of the prior art of small radii and of asubstantial height from the side of the ingot there is a liability oftrapping segregates in these salients due to the rapid formation ofconverging crystals in such old form of salients, since such salientschill quickly and permit the columnar crystals to focus at a pointwithin the portion of the ingot which freezes directly under theinfluence of the chill from the mold wall.

Ingots having relatively high salients of small cross section formed onsmall radii not only trap segregates and cause weakness by entangledcolumnar crystals in the salients, but also tend to decarburize or burnon the tops of the salients when being reheated in the soaking pit forrolling or working. This results in a weakened longitudinal plane at thetop of the salient and the fabricated articles show faults over theseareas in the finished product corresponding to the crests of these smallsalients.

In the present invention the curvature of the recesses and ribs in themold, forming salient and non-salient surfaces on the ingot, are of suchform that the columnar crystals in the ingot which grow at substantiallyright angles to these surfaces do not tend to focus within the zone ofdirect chill of the mold.

The axes of the radii upon which the recesses and ribs'of the mold areformed are so locatedthat when. the ingot is cast therein the columnarcrystals, if extended, tend to come to a focus within the zone of axialcrystals in the ingot. In other words, the radii of the salient recessesin the mold .are such that during the freezing of the ingot, the ingotis entirely frozen before the columnar crystals have grown to suchlength that the inner ends of these crystals overlap or intersect witheach other. This prevents trapping of the concentratesby the ends ofcolumnar crystals as would occcur where the salients on the ingot are ofsuch form as to cause these crystals to actually intersect and focus.

From a crystalline standpoint the radii of the non salient portions onthe ingot is not so important as the radius of the salient portions, butin practice it has been found that non-salient portions should be ofsuch radii as to avoid surface defects which may occur in working theingot when'the non-salient portions are on very small radii and also topermit the free growth of these columnar crystals without bringing theinner ends of these crystals into interlacing contact with each other.

Another important feature of this invention resides in the mold matrixsalient recesses, forming salients on the ingot, being parallel to eachother and to center planes at right angles to the mid sections of themold side walls. This produces salients on the ingot which pass in astraight line direction under the rolls of a rolling mill and preventany cross or diagonal rolling on the surface of the ingot. The dimensionof the salients being uniform throughout the length of the ingot permitsuniform crystallization'of the ingot for the full length of the-ingot.This also obviates non-uniform casting and rolling strains on thesalients and permits uniform heating of the salients when the ingot isin the soaking pit. Where the matrix of the mold is tapered, as may bethe case in rectangular molds, the maintaining of these salient recessesof the same size throughout the length of the mold, and with the bottomsof the salient recesses parallel, may be accomplished by providing smallflat narrow triangular areas on the sides of the matrix mold walls, andthese areas are preferably located between the corner curved surfacesand the adjacent salient recesses.

The present invention also comprises a novel ingot of steel preferablyhaving parallel salients on the ingot surface and with the salientshaving radii located within the portion of the ingot comprising theaxial crystallization zone so that the columnar crystals do not come toa focus, but the inner ends of these crystals comprise a wavy zonesurrounding and securely locked into the axial crystal center portion ofthe ingot.

With ingot molds of the improved construction, several other advantagesalso occur. Some of these advantages are that the corrugated side wallskin of the ingot during pouring and freezing can straighten out orelongate by flattening out the corrugations without causing longitudinalcracks, and since the radii of the salients are relatively large, thedanger of adverse crystallization is overcome, and the danger of burningor decarburization of the tops of the large salients is also overcomesince the mass of metal beneath the salients is sufliciently great toabsorb heat which otherwise would burn the tops of salients of smallradii. A further advantage is obtained by these large radii salients inthat where long vertical ingots are being cast and the upper part of theingot is maintained hot during the latter part of the pouring while thelower part is cooling and tending to rise from the stool, because of theupper part being hot and being tightly wedged to the upper portion ofthe mold, these ribs which have been chilled comprise stays or strutswhich are of sufficient strength to support the downward verticalferrostatic pressure of the molten steel in the ingot and also verticalshrinkage, thereby also hang cracks.

Increased height of salient on an ingot gives increased strength ofingot skin. In rolling practice, however, there is a maximum heightwhich is allowable for any given cross-sectional size of ingot.Moreover, the size of ingot deterobviating the undesirable horizontal ormines the number of proper. salients which may be placed in the sidethereof. Using this proper number of salients and with the form ofcurvature such as will produce correct crystallization, the maximumheight of salient is obtained by having the non-salient radiusrelatively small.

Other and further objects of this invention will in part be obvious andwill in part be pointed out hereinafter by reference to the accompanyingdrawings forming a part of this specification.

Realizing that the present invention may be embodied in structures otherthan those specifically disclosed, it is to be understood that thedisclosure herewith is illustrative and not in the limiting sense.

Fig. 1 is a longitudinal section of the mold in accordance with thepresent invention and wherein the flats on the sides of the mold areshown exaggerated in order to be indicated on the drawings.

Fig. 2 is a cross sectional plan view of the upper portion of a moldwith an ingot cast therein in accordance with the present invention. I

Fig. 3 is a bottom plan view of the lower end of the mold illustrated inFig. 2.

Fig. 4 illustrates detailed portion comprising a section adjacent oneside of an ingot in accordance with the present invention, and with thesalients joined by long non-salient portions.

Fig. 5 is a view similar to Fig. 4 showing these salients joined by ashort non-salient portion.

Fig. 6 is a view similar to Figs. 4 and 5, and wherein the salients areof small radii but low depth.

Fig. '7 is a longitudinal view of a rectangular ingot in accordance withthe present invention showing a portion of the ingot broken away to moreclearly illustrate the relation between the columnar and axial crystals.

Referring now to the drawings and more especially to Figs. 1, 2, and 3,Fig. 1 illustrates a longitudinal or vertical cross section through amold in accordance with the present invention. The mold walls I areprovided with salient recesses 2, which are illustrated in the presentcase as comprising two salient recesses (which number may be increasedas desired) between each corner surface 4, and joined at the mid sectionof the side wall of the mold by a non-salient rib 5. These salientrecesses on the same side of the matrix have their bottom portionsextending parallel throughout the length of the mold, as is indicated bylines 6 and I in Fig. 1. These salient recesses, therefore, formparallel salients on an ingot cast in the mold. In view of the fact thatthe molds as illustrated herewith are slightly tapered and the bottomwidth of the matrix is slightly greater than the top thereof, fiatsurfaces 8 and 9 (shown in Fig. 1 in exaggeration) occur between thecorner surfaces 4 and the adjacent salient recesses 2. These surfacesare referred to as flat but it isunderstood that the term fiat is merelyrelative. They may be somewhat curved, and the construction which isemphasized is that the salient recesses are made parallel. withoutdistortion of the corner surfaces, and with the salient recesses beingof substantially the same width and height throughout the length of themold.

An extremely important feature of the present invention resides in thefact that the salient recesses 2 and nonesalient ribs 5 are so formedthat the growth of the columnar crystals in an ingot while freezing in amatrix will not focus within the zone of mold wall chill. In thepreferred embodiment of the invention, the axes III of the radii II arewithin the zone of axial crystals of the ingot and beyond the normalefiect of chill of the mold on the crystallization of the ingot. Thisinsures that the columnar crystals which grow at substantially rightangles to the surface of the mold do not come to a focus and thereforedo not trap inclusions.

A further advantage of this construction is that the zone where thecolumnar crystals meet the axial crystals in the ingot is such thatthese two types of crystals interlock with each' other in aninterlocking zone which thoroughly ties the two types of crystalstogether. This zone is indicated on Fig. 2 by the dotted line l2, but itis to be understood that the zone is of a relatively substantial widthso that the dotted line indicates the general rather than the absolutedefinite location of the zone.

Fig. 3 illustrates the, bottom of the matrix shown in Fig. 2 and showsthe salient recesses 2 and non-salient ribs to be of the same size andshape throughout the length of the mold.

Fig. 4 is a detailed section of a portion of an ingot adjacent thesurface cast against the salient recesses and showing the salients l4and I5, which are on radii of the same length, the axes of which radiiare located well within the zone of axial crystals IS. The non-salientportion I1 is formed on a relatively long radius and is tangent at itsextremities to the curves of the salients l4 and [5.

Fig. 5 is a view similar to Fig. 4 with salients I4 and I5 thereon beingformed of the same radii as shown in Fig. 4. The non-salient portion l8however, is upon a shorter radius. This forms a deeper salient andprovides additional stiffening in the ingot while the ingot is freezing.This view illustrates the crystallization from surfaces having thesalient portions maintained at proper radii and with the non-salientportion being relatively small.

Fig. 6 illustrates small salients l9 formed upon radii 20, the axes ofwhich are located within the chill zone and with non-salient portions 2|joining the salient portions so that the height of the salientsis'relatively low. While as above specified, the columnar crystals tendto grow at substantially right angles to the mold wall surface,

the actual growth of these crystals is influenced I the growth of thecolumnar crystals 24 from the non-salient portions 2|. Under theseconditions a very few of the columnar crystals 22 growing from thesalients l9 tend to focus at the axes 25 of the radii but the influenceof the growth of the columnar crystals 24 adjacent the salient crystals22 permits a slight swinging outward of these colunmar crystals 22 sothat instead of focusing at the axis 25 the majority of these columnarcrystals extend in a direction which would focus at the point 26 andsome of the columnar crystals 22 tend to focus along the entire linebetween the point 25 and the axis 25 of the radii. It will be observed,however, that the extreme length ofa columnar growth terminatessubstantially ata depth on which the axes 25 are located so that sincethese crystals do not grow beyond the depth indicated by the line 21,there is no substantial interlacing or focusing of any substantialamount of the columnar crystals 22 within the zone of the direct chillfrom the side wall of the mold. This condition obviates end of saidmatrix being of larger cross sectional any cleavage plane being formedin the columnar crystal area in view of the fact that a substantialmajority of the columnar crystals 22 if extended would focus within thearea 28 which represents the axial crystals of the ingot.

Fig. '7 illustrates a portion ofan ingot according to the presentinvention with the sides of the ingot being provided with salients 29and 30 which run parallel, and with the columnar. crystal zone 3|adjacent the sides of the ingot, and with the axial crystal zone 32inthe central portion of the ingot, and with the interlocking zone 34intermediate the columnar crystals and the axial crystals.

The present invention produces ingots having not only improved skinsurfaces, but also are better ingots from a metallurgical standpoint inthat the ingots freeze under conditions which obviate harmful internalstresses and the several forms of steel crystals comprising the ingotare permitted to form more freely and to more freely interlock with eachother without trapping harmful inclusions at the juncture between theportion of the ingot directly influenced by the chill from the mold andthe central portion or non-chilled zone in the interior of the ingot.

Having described our invention, we claim:

1. In a vertical ingot mold, a matrix having salient recesses andnon-salient ribs in the side wall thereof, said recesses extendinglongitudinally of said matrix and being of uniform width throughout'thelength of the mold, and with one end of said matrix being of largercross sectional area than the other end.

2. In a vertical ingot mold, a matrix having salient recesses andnon-salient ribs in the side wall thereof, said recesses extendinglongitudinally of said matrix and being of uniform depth throughout thelength of the mold, and with one area than the other end.

3. In a vertical ingot mold; a matrix having salient recesses andnon-salient ribs in the side wall thereof, the corners of the matrixbeing on a uniform radii throughout the length of the matrix, the bottomportions of said recesses on one side of said matrix eing parallelthroughout the length of said mold, and with said matrix tapering fromone end toward the other.

4. In a vertical ingot mold, a matrix having salient recesses andnon-salient ribs in the side wall thereof, the bottom portions of saidrecesses on one side of said matrix being parallel throughout the lengthof said mold, each of said recesses being of uniform depth throughoutits length, and with said matrix tapering from one end toward the other.

5. In a vertical ingot mold, a matrix having salient recesses andnon-salient ribs in the side wall thereof, the bottom portions of saidrecesses on one side of said matrix being parallel throughout the lengthof said mold, each of said recesses being of uniform width and depththroughout its tween the corners and the adjacent salient recesses.

7. In a vertical ingot mold for casting steel ingots, a matrix portionhaving a vertical taper and with salient recesses and non-salient ribson the side walls thereof, the corners of said matrix being rounded andtapering fiat zones between the corners and the adjacent salientrecesses, said salient recesses located on the same side of said matrixall being parallel throughout the length of said mold. I

8. In a vertical ingot mold for casting steel ingots, a matrix portionhaving a vertical taper and with salient recesses and non-salient ribson the side walls thereof, the corners of said matrix being rounded andtapering fiat zones between the corners and the adjacent salientrecesses, said salient recesses located on the same side of said matrixall being parallel and of uniform depth throughout the length of saidmold.

9. In a vertical ingot mold for casting steel ingots having a matrixwith longitudinally extending salient recesses and non-salient ribs inthe side wall thereof, the matrix being tapered from one end of the moldto the other, said recesses and ribs being of uniform depth, width, andcurvature throughout the length of the mold, the corners of said matrixbeing rounded and with narrow fiat triangular zones adjacent saidcorners.

10. In a vertical ingot mold for casting steel ingots having a matrixwith longitudinally extending salient recesses and non-salient ribs inthe side wall thereof, the matrix being tapered from one end of the moldto the other, said recesses and ribs being of uniform depth, width, andcurvature throughout the length of the mold, the corners of said matrixbeing rounded on a uniform radius throughout the length of the mold, andwith narrow flat triangular zones adjacent said comers.

11. An ingot mold having a longitudinally tapered matrix with salientrecesses and nonsalient ribs on the walls thereof, the corners of thematrix being of uniform radius throughout the length of the matrix, thesalient recesses in the side walls being formed on a uniform radiusthroughout the length of the matrix, and the axes for the radii of thesalient recesses on a side of the matrix being parallel to each other.

JOHN E. PERRY. WILLIAM HAIG RAMAGE.

